Agricultural crops are susceptible to a large variety of microbial pathogens, which results in annual losses and economical damages. Methods developed to protect crops from plant diseases include plant breeding for resistance, cultural practices, application of chemical agents, and biological control.
As the use of chemical pesticides resulted in severe environmental pollution, and many pathogens are developing resistance to existing chemicals, many pesticides are now banned for use, and organic farming is not allowed to rely on such substances at all. Thus, a major goal, therefore, is to develop new, environmentally-friendly tools to control pathogens, namely, biological control techniques.
U.S. Pat. No. 6,495,133 describes a strain of Glicladium roseum exhibiting antagonistic effects against plant pathogens. The biocontrol agent is used in treatment to seeds, soil or plants to protect against fungal pathogens of various plants, including tomato.
US patent applications publications Nos. US2011028500 and US2011014596 describe a plant pathogen inhibitor combination comprising a plant extract containing one or more anthraquinone; an anti-phytopathogenic agent which may include natural oil or oil product having fungicidal activity.
Indian Patent Application No. IN03603CH2010 describes an invert-emulsion formulation of fungal organisms as biological control. The formulation is in the form of an invert emulsion formulation. The process described includes production of fungal spores either by solid state or liquid fermentation; preparation of conidial suspension or cell suspension; preparation of aqueous phase by mixing the conidial suspension, water, emulsifier and glycerol; preparation of oil phase by adding vegetable fat mixture to a warm vegetable oil mixture; mixing of aqueous phase with oil phase to get water in oil or invert-emulsion formulation using homogenizers The product can be used for seed treatment, soil application and foliar spray.
U.S. Pat. No. 7,485,451 also describes an invert emulsions (water in oil emulsions) comprising cellular material selected from living and/or dormant prokaryotic and/or eukaryotic cells and tissues, the cellular material being compatible with water-in-oil emulsions. Examples of cellular material included fungi, watermolds, algae, yeasts, bacteria, plant, inset and animal cells. The inverted emulsion also comprises an oil, such as vegetable oil and/or fish oil as well as an oil soluble non-ionic surfactant, and water. Optionally, the composition contains a thickener, such as fumed silica or bentonite.
Essential oils having an antagonistic effect have also been investigated. For example, the antibacterial activity of Moroccan plants extracts against Clavibacter michiganensis subsp. Michiganensis (CBM), the cause of tomato bacterial canker, was described [Ait Ben Aoumar A. et al. J. Med. Plants Res. 6(17):4332-4338, 2011]. In addition, the effectivity against CBM of plant essential oils from 34 aromatic plants was examined [Pouvova D. et al. Zemdirbyste-Agrucyktyre 95(3):440-446, 2008].
Recently, the simultaneous production of DAPG and HCN by Pseudomonas sp. LBUM300 was found to be beneficial for the biological control of tomato bacterial canker caused by Clavibacter michiganensis subsp. michiganensis [Lanteigne C. et al. Phytopathology. 102(10):967-73, 2012].
In addition, attempts at biological control of CBM Rockwool-grown greenhouse tomatoes was described. Specifically, artificial inoculation of two and three years old rockwool slabs with CBM bacteria dead plants reduces death rate of the plants [Slusarski C. Vegetable Crop Research Bulletin 69:125-134 2008].